Currently, 2,2-dichloro-1,1,1-trifluoroethane (also referred to as “HCFC-123” in the present specification) is used as a low-pressure refrigerant for large chiller refrigerators, particularly for turbo refrigerators.
However, HCFC-123 is a hydrochlorofluorocarbon (HCFC) containing chlorine in the molecule, and its use is being banned to protect the ozone layer.
Therefore, the replacement of HCFC-123 by new refrigerants using hydrofluorocarbons (HFCs), which do not contain chlorine in the molecule and have an ozone-depleting potential (ODP) of 0, is ongoing. However, HFC refrigerants are very stable and thus have a high global warming potential (GWP). In recent years, reduction of the use of HFC refrigerants, including the EU F-gas regulation, has been promoted to protect the global environment. Accordingly, HCFO (hydrochlorofluoroolefin) refrigerants are being developed as low-GWP refrigerants. The HCFO refrigerants contain HFO (hydrofluoroolefin) and chlorine, but have a short atmospheric life because they have a double bond. Further, these refrigerants have not only a very low GWP but also a very low ODP.
For example, PTL 1 proposes that HCFO-1233zd(E) can be used as an alternative refrigerant for HCFC-123, and refers to HFC-245fa as a refrigerant that may be optionally added; however, the mixing ratio thereof is not shown. Moreover, PTL 2 proposes an HCFC-123 alternative refrigerant comprising at least 50 wt. % of HCFO-1233zd(E) as a composition of a heat transfer medium.